1- What is jQuery ?
It's very simple but most valuable Question on jQuery means jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, animating, event handling, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript. Jquery is build library for javascript no need to write your own functions or script jquery all ready done for you

2- How you will use Jquery means requirement needed for using jquery?
Nothing more need to do just olny download jquery library(.js file) from any of the jquery site Download jquery and just linked with your html pages like all other javascript file

3- what the use of $ symbol in Jquery?
$ Symbol is just replacement of jquery means at the place of $ you may use jquery hence $ symbol is used for indication that this line used for jquery

4- How do you select an item using css class or ID and get the value by use of jquery?
If an element of html like < div> , < p> or any tag have ID MyId and class used MyClass then we select the element by below jquery code

Code:

$('#MyId') for ID and for classs $('.MyClass')

and for value

Code:

var myValue = $('#MyId').val();

// get the value in var Myvalue by id
Or for set the value in selected item

Code:

$('#MyId').val("print me");

// set the value of a form input

5- How to get the server response from an AJAX request using Jquery?
When invoking functions that have asynchronous behavior We must provide a callback function to capture the desired result. This is especially important with AJAX in the browser because when a remote request is made, it is indeterminate when the response will be received.
Below an example of making an AJAX call and alerting the response (or error):

1) How does adding jquery js from google cdn differ from hosting it on server itself?
Ans: If you have website then it makes sense to add it from google cdn as it will get automatically downloaded. But if you have a application which will not run machines with internet connection then use locally hosted jquery js.
2) When and why should we use minified version of jquery js?
Ans: The minified version saves bandwidth and hence improves performance of the website/web application. The minified version is recommended to be used in production environment.